A major focus of robotic applications is the development and control of devices that are capable of gripping and manipulating materials. Basic grippers consist of two surfaces that can be brought together; more dextrous grippers use fingers, some of which can be individually controlled as disclosed in Causey, G., Guidelines for the design of robotic gripping systems. Assembly Automation, 2003, 23: p. 18-28; Marcincin, J. N. and J. Smrcek, Biomechanical grippers: important elements of biomechanical robots. Industrial Robot, 1997, 24: p. 234-238; and Arimoto, S., K. Tahara, M. Yamaguchi, P. Nguyen, and H.-Y. Han, Principles of superposition for controlling pinch motions by means of robot fingers with soft tips. Robotica, 2001, 19: p. 21-28. For rigid objects, grippers usually fall into two broad classes: friction grippers or encompassing grippers, as disclosed in the Causey article. If the gripper uses the friction between its surfaces and the object to grip it, the gripper requires about four times the force of an encompassing gripper, whose surfaces partially conform to those of the held object, as disclosed in Zajac, T. J., Robotic Gripper Sizing: The Science, Technology and Lore. http://www.grippers.com/size.htm, 2002.
Holding and manipulating soft or delicate materials is an area of intense research. A recent survey of devices that could grip materials such as fabrics, leathers, or food products found three major categories: pinching using friction (similar to the principles described above), intrusive grippers that insert pins into the material to lock it in place, and surface attraction grippers that make use of adhesives or vacuum, as disclosed in Taylor, P., Presentation and gripping of flexible materials, Assembly Automation, 1995. 15: p. 33-35. A difficulty with such prior art devices is that they may crush, deform, or in other ways change the properties of the object that has been gripped. Thus, it would be of great value and interest to develop grippers that could handle soft, pliable, fragile, slippery and irregular materials without inducing significant material deformation.
Biological organisms are frequently confronted with highly complex materials that they must manipulate to achieve their goals. For example, animals that feed on seaweed must be capable of harvesting large amounts of slippery, irregularly shaped material that is usually connected to a substrate by a holdfast. Many organisms have successfully solved these problems using a variety of different feeding-mechanisms. One very successful group is the mollusks, which are capable of feeding on highly irregular materials using a feeding apparatus known as the radula (rasper) controlled by underlying musculature (the odontophore) and moved forward and backward by other muscles in order to contact food, and then convey food into the animal's body, as disclosed in Brusca, R. and G. Brusca, Invertebrates. 1990, Sunderland, Mass.: Sinauer Associates, Inc, p. 728-738.
The sea slug, Aplysia californica, uses a muscular structure called the buccal mass to grasp and ingest food. As shown in FIG. 1, the central grasper within the buccal mass consists of a thin, flexible surface covered with fine teeth (the radula), that is opened or closed by a set of muscles known as the odontophore. The structure is moved towards the jaws (protracted) using a thin, sheet like muscle (I2), and can be moved towards the esophagus using thick bands of muscle that form the jaws (I1/I3 jaw muscles), as disclosed in Kandel, E., Behavioral Biology of Aplysia, 1979, San Francisco: W. H. Freeman and Co., p. 88-96; Kupfermann, I., Feeding behavior in Aplysia: A simple system for the study of motivation; Behav. Biol., 1974, 10: p. 1-26; and Neustadter, D., R. Drushel, P. Crago, B. Adams, and H. Chiel, A kinematic model of swallowing in Aplysia californica based on radula/odontophore kinematics and in vivo magnetic resonance images. J exp Biol, 2002. 205: p. 3177-3206.
U.S. Pat. No. 6,764,441 and Mangan, E. V., D. A. Kingsley, R. D. Quinn, and H. J. Chiel, Development of a peristaltic endoscope. International Congress on Robotics and Automation 2002, 2002: p. 347-352, disclose a self-propelled device capable of peristaltic locomotion caused by a plurality of braided pneumatic actuators that surround a central flexible tube. This device demonstrates the use of braided pneumatic actuators for locomotion, whereas the device disclosed in this application demonstrates the use of these actuators for gripping and manipulating flexible and irregular materials. Moreover, the braided pneumatic actuators in that application are arranged in series, and thus are not used in the same form as disclosed in this application.